Animal collars having ectoparasiticidal activity have been known for some years. By using them, it is possible to protect animals and, in particular, small animals (especially dogs and cats) against infestation by Mallophaga and Siphonaptera and, in some cases, against Ixodidae.
In general, the ectoparasiticidally active animal collars available consist of thermoplastic polyvinyl chloride, into which an insecticidal active compound, usually O,O-dimethyldichlorovinyl phosphate (DDVP), has been incorporated by co-extrusion with the polyvinyl chloride. However, collars based on DDVP lead to the occasional occurrence of skin irritation on the animal. Additionally, the relatively short life of the collar as a result of the relatively high vapor pressure of DDVP (1.2.times.10.sup.-1 mm Hg) is also a disadvantage.
Animal collars based on plasticized thermoplastic polymers (preferably plasticized polyvinyl chloride) and which contain the less highly volatile carbamates as insecticidal active compounds are known and are described in U.S. Pat. No. 3,852,416. Whereas highly volatile active compounds such as DDVP rapidly pass directly into the gas phase from the ectoparasiticidally active plastic collars, insecticides of lower volatility, such as the above-noted carbamates, diffuse slowly out of the collar and form a white, dusty layer on its surface. Some of the active compound passes into the vapor phase by sublimation and is active there and some is distributed, in the form of a dust, over the animal to be treated.
The deposition of the active compound on the surface of the collar (known as "efflorescence" or "exudation") is associated with a number of disadvantages:
(1) When the collar is stored for a prolonged period before use, a relatively large amount of the active compound diffuses to the surface and becomes concentrated there. When the collar is used, there is then a very high dose of the insecticide on the surface, which while ensuring good immediate action, may also reach the point of being toxic to the animal.
(2) While the active compound present on the surface is rubbed off rapidly, the active substance in the deeper layers of the collar diffuses to the surface very slowly. Thus, the release of the insecticide is not linear over as long as possible a period as is desired and/or necessary.
(3) Finally, the dusty, whitish active compound present on the surface of the animal collar imparts an extremely unattractive, dusty or moldy appearance to the collar.
Plasticized polymers (such as, e.g. vinyl polymers, polyesters, polyurethanes and epoxide resins) are known and are described as carriers for various insecticides in French Pat. No. 1,568,194. The materials are employed in the form of a tape or powder, for example, for combating insects. Carbamates are not mentioned among the suitable insecticides disclosed therein.
Pulverulent, water-soluble vinyl polymers which contain various active compounds, including carbamates to be used as insecticides; are also known (see, e.g. U.S. Pat. No. 3,576,760). These polymer powders make it possible to apply an active compound in the dry form, for example to the earth's surface, where it is then released through the action of water.
U.S. Pat. Nos. 3,822,238 and 3,975,350 relate to hydrophilic, water-absorbing polyurethanes and polyurethane hydrogels and their use as carriers for various active substances. Insecticides are mentioned quite generally as such active compounds (for example those described in U.S. Pat. No. 3,576,760). However, the materials described therein would be unsuitable for the purposes of the instant invention because of their swellability in water.